Data vanishes from portable hard drive.

So,

After recently acquiring a new hard drive, I have been meaning to sort through my personal data (photos, videos, docs), in order to get my new device a fresh start. I did backup all of the folders on my portable hard drive, but now I seem to have lost a chunk of them.

I copied all of the independent folders from C: to F:, verified that all was there, and then proceeded to delete the duplicates on my main drive. Verified that all was there again before emptying the bin, in case of some shortcut mishap, but all was good, so I carried on with my business.

I have used the said files since, but two days ago, everything dated from March 2010 to September 2010 has vanished. I am at loss...

I have tried recovering my files, but not only do they no show in the portable drive's lost data, they aren't in the recycle bin from the main drive either. I have deleted them, last week, and haven't installed anything else since. I have also tried uncovering them, but they weren't hidden... What is going on!?!

Digging into partitions this afternoon, I have found the files to appear on the second partition of my main drive, but none of the files are salvageable. It still would not explain why the files have suddenly vanished from the portable drive. I have also found that my restore points were not automatically scheduled, so I don't have anything to work with, not that I'm convinced that it would make anything reappear.

Thanks for your patience, any help would be greatly appreciated.


Specs:
Windows 7 64-bits
Norton 360
2 serial drives
1 portable Western Digital
1 new drive, that has mainly been used to recover what I could from all this mess...